Cylinders are commonly used for storage and supply of liquefied petroleum gas (LPG), where the LPG is stored under pressure and in a liquid form. The gas cylinders are used by, in particular, owners of gas-fired barbeques, gas-fired patio heaters, and gas heated spa pools, in situations where there is no connection to a reticulated gas main. Where there is no gas main available, gas cylinders are the only means of supplying LPG for ordinary household applications such as cooking and heating, and indeed for business and commercial use for these purposes.
Cylinders typically have a body of cylindrical configuration tending to a rounded/dome shaped base and top portion, formed integrally therewith. The cylinder has a footing at the base thereof, formed integrally therewith, usually welded to the base. The footprint of the footing is less than the diameter of the cylinder, but sufficiently wide to provide stability. The footing is often a ring-like member attached coaxially with the cylinder at typically three or four points spaced equidistant around the base. The cylinder is provided with a guard attached coaxially with the cylinder to the top portion, the guard being usually a ring-like configuration, attached to the top of the cylinder. The guard provides protection against breakage or other damage to fittings through which gas is drawn off, in addition to providing a handle in the form of a hand-hold aperture by which the cylinder may be picked up and carried. The guard and footing are typically attached in a manner that prescribes a circle at each end of the cylinder, the circles having a circumference less than the maximum circumference of the body. In this specification the prescribed circle that the guard forms where attached to the top portion of the cylinder shall be referred to as the guard circumference, and the prescribed circle that the footing forms where attached to the base of the cylinder shall be referred to as the footing circumference.
Gas cylinders are certified for a period of ten years, after which it is necessary that they undergo a full inspection and refurbishing, and if passed are certified for a further ten year period.
In the case of smaller cylinders, commonly referred to as 4.5 kg and 9 kg cylinders, when the cylinder is empty or nearly empty, it is a common practice for the owners to take the cylinder to a depot or fuel outlet such as a petrol station, and refill the cylinder. The onus is on the depot or outlet to ensure that an out-of-test cylinder is not refilled.
More recently cylinder exchange services have become popular, where when a gas cylinder is empty or near empty, for a fee the consumer simply swaps the cylinder for a full cylinder, at the retail outlet. With cylinder exchange services, the onus does not rest with the consumer to maintain the certification of the cylinder, but rather rests with the service provider. As the exchanged cylinders have often been knocked around and/or left outside in the elements, on receipt of the empty cylinders, the service provider is required to refurbish the cylinders before they are refilled with LPG. This involves stripping of paint on the cylinder and removal of any surface rust, before the cylinder is repainted, relabelled and clad with a expanded-mesh plastic netting to prevent the paint being chipped by adjacent cylinders coming into contact with each other. Any cylinders that are out-of-date must first be recertified, which involves an internal inspection to ensure that there is no corrosion present and pressure testing. Subsequent to refurbishing, the cylinders can be refilled with LPG.
As can be appreciated, there is a high cost associated with the above described process. It is labour intensive and requires a lot of material, especially in terms of consumables such as paint and thinners, and supplies for stripping the old paint. The use of volatile organic compounds particularly in the form of thinners used in the spray painting process is of some concern, not only from the point of view of risk of fire and other accidents involving personnel, but also pollution of air from evaporation and ground water from spillage.
In view of the foregoing, it would be desirable to provide an alternative that could cut down on the amount of paint required in the refurbishing of cylinders.
Throughout the specification, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.